What is the formal definition of 'opposite sides' of a polygon? Does a
regular pentagon have opposite sides? Does a concave polygon have
opposite sides? How can we define it consistent with our intuition?

I have a grid containing 16 squares. Each square represents 1 acre. I
need to draw 11 sections of fence along the dotted lines of the
squares so that 4 fields are formed, each containing 4 acres of land.

How can I estimate how many chairs can be placed in the seating area of a
convention center meeting room that is 80 feet across at the front, 120
feet across at the rear, and 150 feet from front to back?